Solve This integral and check it with my answer

Question

anonymous · Answer

$$\int\limits_{?}^{?}x^3dx/\sqrt{4+x^2}$$

myininaya · Answer

use a trig substitution
let $$\tan(\theta)=\frac{x}{2}$$

anonymous · Answer

true how'd you come to the conclusion to use tan = x/2 or did you just use if 4+x^2 = 2tan(theta) and then just solved for tan?

myininaya · Answer

well there are only really 3 substitutions you need
the others are just repeats 
i will show you why i knew this
but i have to do it on paper and then i will scan and post

anonymous · Answer

alright. I'm just wondering

I know the equations, just sort of wondering how you came to the conclusion x/2 = tan without coming to the conclusion first that x=2tan(x)

myininaya · Answer

i will show you on paper

myininaya · Answer

attachment

anonymous · Answer

never got an answer to check with mine

myininaya · Answer

you never asked lol
just you asked me to explain why i used that substitution

anonymous · Answer

what do you get for an answer?